Catalyst and process for the production and regeneration thereof



Patented Oct. 15, 1935 UITED ST CATALYST AND PROCESS FOR THE PRO- DUCTION AND REGENERATION THEREOF Eugene Dwight Crittend Signor to Atmospheri en, Syracuse, N. Y., as-

Nitrogen Corporation,

New York, N. Y., a corporation of New York No Drawing. Application November 13, 1930, Serial No. 495,539

16 Claims. (01. 23-162) This invention relates to a process for the production of catalysts. More particularly, this invention relates to a process for the production of a pure cobalt metal and to the production therefrom of a cobalt oxide contact material for catalyzing the oxidation of ammonia by means of oxygen.

It has heretofore been proposed to oxidize ammonia by passing it together with oxygen in contact with a heated catalyst consisting of cobalt oxide. Such a catalyst may be prepared by dissolving cobalt metal in nitric acid to form a solution of cobalt nitrate and preparing the catalyst from such a solution. It has, however, been heretofore considered that cobalt oxide alone is a relatively poor catalyst for the oxidation of ammonia, and in commercial practice resort has been had to catalysts comprising cobalt oxide together with a promoter. It has recently been discovered, however, that pure cobalt oxide without a promoter is a highly active and eflicient catalyst for ammonia oxidation. I have found, however, that in preparing catalysts from commercial cobalt metal, it frequently happens that the catalyst has but a relatively low activity in catalyzing the oxidation of ammonia. Furthermore, it frequently happens that a cobalt oxide catalyst which has been used for a period of time for the oxidation of ammonia loses its activity due to the efiect upon the catalyst of impurities in the gas, because of the catalyst being exposed to too high temperatures, orfor other reasons.

I have discovered that by subjecting to a fusion purification, commercial cobalt metal or cobalt oxide which yields a relatively poor catalyst or spent cobalt oxide catalyst, e. g., catalyst which has deteriorated in use, the resulting cobalt metal may be used for the production of a highly active catalyst.

It is, accordingly, an object of this invention to provide a process for the purification of cobalt, starting either with the metal or with the oxide, whereby metallic cobalt is obtained which, upon treatment for the production of a contact material therefrom, yields an eflicient highly active catalyst for the oxidation of ammonia.

The invention comprises treating fused cobalt metal at an elevated temperature with a flux, separating the fused metal from the slag which forms and converting the thus treated metal into a catalyst. When the cobalt is originally in the form of cobalt oxide, the invention further comprises reducing the cobalt oxide to cobalt metal The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others and the catalyst possessing the features and properties, which are exemplified in the following de- 5 tailed disclosure and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description of a process 10".

for treating cobalt oxide material for the production of a. catalyst therefrom. For purposes of illustration, the invention will be described as applied to the regeneration of a cobalt oxide which has been used for the oxidation of ammonia and has become relatively inactive by reason of its being poisoned by impurities in the gas or for some other cause. It is to be understood, however, that the invention is not limited in any way to the treatment of such a material, but is likewise applicable to cobalt oxide from other sources, or as will be particularly pointed out below to cobalt metal.

The cobalt oxide is first ground until the most of the material will pass through a 100 mesh screen. It is then mixed with about 17% to 19% of its weight of carbon, for example powdered coke or wood charcoal, and the mixture made into a heavy paste with a solution of sugar in water. A suitable solution is one containing about one part of sugar to every 5 parts of water 7 by weight. This solution is added to the mixture in the proportions by weight of about 6 parts of the solution to about 15 parts of cobalt oxide in the mixture. The paste is granulated to form coarse granules and the granules dried by hea, n mg.

A portion of the granulated material is charged into an electric furnace arranged for heating by an electric arc and provided with carbon elec- 40 trodes. An arc is established between the electrodes and positioned so as to heat the mixture. Under the influence of the high temperature, the cobalt oxide is reduced by the carbon and a pool of molten metallic cobalt forms.

After a quantity of molten cobalt metal is formed in the furnace, a flux consisting of a mixture of coarsely ground limestone (having a particle size of, for example 2 to 10 mesh) and powdered calcium fluoride are added in sufficient amount to cover the pool of molten metal. Suitable proportions of the flux materials are 3.5 to 5 I parts of limestone to 1.7 to 3.5 parts of calcium fluoride for every 100 parts of cobalt oxide. Ad

1 ditional quantities of the granulated mixture of cobalt oxide, carbon and sugar are periodically point, i. e., it should be one which fuses in confed to the pool of metal in the furnace, together tact with the molten cobalt. Furthermore, it

with additional quantities of the flux, suificient should be basic in character. In using fluxes to keep a clean metal surface. The slag which containing an acidic constituent, therefore, the

5 forms on the surface ofthe pool of metal is reamount of this constituent should be so propor- 5 moved from time to time. 7 tionen that the resulting slag is not acidic. It is,

When all of the oxide for a given run has been of course, apparent that the flux should not be reduced and melted, a small quantity of powdered one which will introduce deleterious substances cobalt oxide containing substantially no carbon into the cobalt treated therewith.

10 is added in amount sufiicient to lower the carbon I claim: 10 content of the fused metalto the desired percent- 1. The process of preparing a catalyst for the e- I as b en found desir b e to main i a oxidation of ammonia which comprises treating carbon content of the cobalt of the order of .1% cobalt metal containing impurities heated to o 1885- Afte removing a l o the a W c fusion with calcium carbonate and calcium forms and adjusting the carbon content of the fluoride in proportions of about 3.5 to 5 parts of 15 metal y addition of Cobalt Oxide, the heating is calcium carbonate and 1.7 to 3.5 parts of calcontinued for a short time, to 30 minutes for cium fluoride fo ve 70 pafts of cobalt, epap d h us d m tal t dr pp d into rating the thus treated metal from the slag and Water to form cobalt Shot or so difie in d v d converting the separated metal into cobalt oxide.

20 form in y Other desired manner- 2. The process of preparing a catalyst for the 20 When the material to be trea ed S in the oxidation of ammonia which comprises treating form of metallic cobalt instead of cobalt oxide, b h; t l containing impurities heated to the above de c be procedure iS modified by fusion with calcium carbonate and calcium omitting the admixing with carbon and sugar. fl oride to form a, slag, separating the thus The cobalt metal is charged into the electric t t metal from'the lag dissolving t sepa- 25 fu ce a d h a ed to s a portion of it. After rated metal in nitric acid to form a solution of a Small q y of the metal has b melted, cobalt nitrate, recovering cobalt nitrate from t e. f ux s added i h p p o of about the solution, and heating said cobalt nitrate to to 5 parts of limestone and 1.7 to 3.5 parts of decompose t and form cobalt ide,

calcium fluoride for every '70 parts of metal. 3 The process of preparing cataiysi; for th so More metal m y be added from time to time oxidation of ammonia which comprises heating gether with additional flllX as required to maina mixture of cobalt oxide containing impurities tain a C ean ta Surface of the fused P and carbon to a temperature at which the oxide W the W Charge is molten, a Small amount is reduced and fused metallic cobalt formed,

of cobalt oxide is added to remove carbon distreating the fused metal t a flux t form a solved from the electrodes and the slag removed slag separating th th t t d m tal from the from the surface of the molten metal. The puril nd converting the separated metal into fied metal may then be converted into shot or n; oxide otherwise cooled as described above. The metal 4 The process of preparing a, catalyst for the 40 is particu a ly e of p s calcium and oxidation of ammonia which comprises heating a or arsenic and t iS a y to the TemOVal Of these mixture of cobalt oxide containing impurities and similar impurities that I attribute the value and carbon t a temperature t ich the oxide of my process. is reduced and fused metallic cobalt formed.

The pu ifie c ba metal may be converted treating the fused metal witha basic flux to form into a cobalt oxide catalyst by any of the well 513g, e t g th t t t t l from 45 known methods- I ma a Catalyst the the slag, and converting the separated metal into oxidation of ammonia, it is preferred to dissolve Cobalt i the cobalt metal in nitric acid to form a solution 5 The process for preparing b lt talyst, of cobalt nitrate. Af e filtering Off any undiswhich comprises heating a mixture of cobalt solved residue, the solution is evaporated and oxide containing impurities and carbon to t 50 the Cobalt nitrate heated at gradually increasing perature at which the oxide is reduced and fused empe t s t decompose the nitrate and form metallic cobalt formed, treating the fused metal Cobalt OXide- A final temperature of heating of with calcium carbonate and calcium fluoride to about 400 C. has been found satisfactory. The form a slag, separating the thus treated t cake of cobalt oxide thus obtained is broken up from the Slag and treating Said metal to com unto particles of a desired size which are placed Vert it into an active catalyst in a suitable vessel. The catalyst is heated and The process for preparing a cobalt catalyst,

mixture of air and 9 about which comprises heating with carbon cobalt 9% ammoma 15 passed m g f s y g 2%; Camoxide containing impurities to reduce the oxide lycst i" tempgmture of on to cobalt metal, treating said metal heated to moma 1s oxldlzefi by the Pif the an 3 fusion with a flux to form a slag, adding cobalt form oxides of mtrogep recover; oxide to the fused metal to regulate the carbon or may be converted m o m me am as may 8 content thereof, separating the thus treated desired. metal from the slag and treating said. metal to 65 Smce certam changes may be made m carry convert it into an active catalyst.

ing out the above process without departing from 'the scope of the invention, it is intended that all a Process for preparme a e f matter contained in the above description shall mat W Pp adm1x1ng be interpreted as illustrative and not in a limitcobalt Oxide eeiitammg p t e wi h fi y ing sense. Other fluxes than the above dedivided carbon. moistenine e mixture t scribed mixtures of calcium carbonate and cala Solution of Sugar. grenlllatmg the moiscium fluoride may be used, for example, mixtures t ned m xtur and dryi t nu a p i of calcium carbonate and silica, or a mixture of heating the granulated mixture to a p calcium carbonate, calcium fluoride and silica., ..t11re at which the oxide is reduced and fused The flux employed should have a proper melting metallic cobalt formed, treating the fused metal 75 with a basic flux to form a slag, and separating the thus treated metal from the slag.

8. In a process for preparing a cobalt oxide catalyst for the oxidation of ammonia, that improvement which comprises admixing finely divided cobalt oxide containing impurities with powdered coke in the proportions of about 17 to 19 parts of coke to every 100 parts of oxide, moistening the mixture with a solution of sugar, granulating the moistened mixture to form coarse granules, drying'the granulated material, heating the dried material to a temperature at which the cobalt oxide is reduced and fused metallic cobalt is formed, treating the fused metal with calcium carbonate and calcium fluoride to form a slag in the proportions of about 3.5 to 5 parts of calcium carbonate and 1.7 to 3.5 parts of calcium fluoride for every 100 parts of cobalt oxide, adding to the fused metal cobalt oxide to regulate the carbon content thereof, and separating the thus treated metal from the slag.

9. The process of preparing a cobalt oxide catalyst for the oxidation of ammonia which comprises treating cobalt metal containing impurities heated to fusion with a basic flux in the proportions of about 5 to 8 parts of the flux for every 70 parts of metal, separating the thus treated metal from the slag formed and treating the metal to convert it into cobalt oxide.

10. The process of regenerating spent cobalt oxide catalyst for the oxidation of ammonia which comprises reducing said catalyst to metallic cobalt, treating the metal heated to fusion with a flux, separating the thus treated metal from the slag, and converting the thus separated metal into cobalt oxide.

11. The process of regenerating spent cobalt oxide catalyst for the oxidation of ammonia which comprises mixing said spent catalyst with carbon, heating said mixture to a temperature at which the oxide is reduced and fused metallic cobalt formed, treating the fused metal with calcium carbonate and calcium fluoride to form a slag, separating the thus treated metal from the slag, and converting the separated metal into cobalt oxide.

12. The process of regenerating spent cobalt oxide catalyst for the oxidation of ammonia which-comprises admixing said catalyst in finely divided form with powdered carbon in the proportions of about 17 to 19 parts of carbon to every 100 parts of cobalt oxide, heating said mixture to a temperature at which the oxide is reduced and fused metallic cobalt formed, treating the fused 5 metal with calcium carbonate and calcium fluoride in the proportions of about 3.5 to 5 parts of calcium carbonate and 1.7 to 3.5 parts of calcium fluoride for every 100 parts of cobalt oxide, adding to the fused metal cobalt oxide to regulate 10 the carbon content thereof, separating the thus treated metal from the slag, dissolving the separated metal in nitric acid to'form a solution of cobalt nitrate, recovering cobalt nitrate from said solution, and heating said cobalt nitrate to a teml5 perature at which the nitrate is decomposed and cobalt oxide formed.

13. The process of oxidizing ammonia which comprises contacting a gas containing ammonia and oxygen with a catalyst prepared by treating 20 cobalt metal containing impurities heatedto fusion with a flux to form a slag, separating the thus treated metal from the slag and treating said metal to convert it into a cobalt oxide catalyst active for the oxidation of ammonia. 25

14. The process of oxidizing ammonia which comprises contacting a gas containing ammonia and oxygen with a catalyst prepared by treating cobalt metal heated to fusion with a flux to form a slag, said metal containing an impurity from 30 the group consisting of phosphorus, calcium and arsenic materials, separating the thus treated metal from the slag and converting the separated metal into cobalt oxide.

15. The process of oxidizing ammonia which comprises contacting a gas containing ammonia and oxygen with a catalyst prepared in accordance with the process of claim 10.

16. The process of oxidizing ammonia which comprises contacting a gas containing ammonia and oxygen with a catalyst prepared by treating cobalt metal containing impurities heated to fusion with a basic flux to form a slag, separating the thus treated metal from the slag and treating said metal to convert it into a cobalt oxide catalyst active for the oxidation of ammonia.

' EUGENE DWIGHT CRITTENDEN. 

